Temperature responsive control



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ROOM THERMOSTAT 8l! fk/VER Moro/e f f A? attorneys Patente-d Sept. 2, 1941 TEMPERATURE aEsroNsrvE coNTaoL William H. Hutchins, Rochester, N. Y., assignor to General Motors Corporation, Detroit, Mich.,.a

corporation of Delaware Application February 26, 1937, Serial No. 127,819

(Cl. 20G-138) 2 Claims.

This invention relates to control apparatus and more specifically to apparatus for controlling a fluid fuel supply device such as, for example, an oil burner.

In the normal operation of an automatic heating plant of any type it is of course essential to have some automatic control within the space to be supplied with heat which broadly opens and closes a circuit to the means supplying fuel to a combustion chamber as the necessity for heat arises and is then supplied. f

With the different types of fuel feeding devices it is also necessary to include in this general control various safety means which take care of any abnormal operation of the system due to various factors.

The normal operation as outlined above would be for the fuel supplying device to start supplying heat to the combustion chamber for a desired time andthen stop. .However there may be some reason why :the device does not commence to burn and in this case it is not' desirable to force fuel into the combustion chamber if the same is not burning as it will merely tend to collect in pools in the case of fluid fuel or in a mass in the case of solid fuel. It is therefore necessary to provide some means for only maintaining the fuel supply means in operation for a predetermined period if it does not start.

There is also the case of thel flame failure for some reason or another in the case of fluid fuel burners after the burner has ignited and is operating normally. In this condition some safety means must be supplied. A second case is that of a momentary current failure either during the starting period or as the burner is in normal operation and there should be some safety means to prevent an explosion following a momentary current failure which would of course extinguish the flame. l

It is therefore an object of my invention to provide a control for uid fuel burners which includes and embodies .the necessary control and safety factors l.as outlined above.

It is a further object of my invention to provide a compact and rugged master control to be utilized in this type of control system.

With these and other objects in view.` the embodiments of my invention are described in the following specification and claims and illustrated in the accompanying drawings, in which;

Figure 1 is a side elevation of the master control of my invention.

Figure 2 is an enlarged end elevation of the control, a portion being broken away.

Figure 3 is a sectional view taken on line 3 3 of Figure 2.

l circuit to which the master control shown in the drawings is connected for motorv operation.

The master control designated generally at 2 is composed of a flanged plate 4 which may be termed the backing plate to which is secured adjacent the central portion a hollow cylindrical member 6 the ends of which are flattened radially y to lie adjacent the plate 4 and are secured thereto by riveting or other suitable means. The cylindrical member 6 has welded thereto a fiat bar 8 which extends outwardly from the plate at right angles and has an vend portion Ill bent at a right angle theretoand supporting one end of a compound bim'etallic member I2 the opposite end of which is supported on a rod I4 longitudinally movable through an opening I6 in the end of the cylindrical member 6 and also through an opening I8 in the plate 4. Therefore as the heat applied to the bimetallic member I2 changes, it

will cause the rod I4 to move in either direction longitudinally.

Supported on the opposite-face of the flanged plate 4 is an insulating plate 28' secured to the flanged plate 4 by suitable spacing screws 22, said plate having adjacent its center a circular opening within which is secured a bushing 24 having a shoulder fitting snugly on the plate on one side and being externally threaded for a supporting nut 26 on the opposite side and through said bushingthe rod I4 projects 'to operate various mechanism carried on the plate.

Secured in parallel spaced relation with the insulating `plate 2li is a second plate 28, which is held in its proper spaced position by suitable spacing elements 30 and bolts 32. Between the two -plates and secured rigidly to the upper or outer plate 28 is a small motor 34 which may be .of the synchronous type. The rotatable shaft 36 of the motor projects through the plate 28 and has rigidly secured thereto for rotation a cam disk 38 by' a set. screw 40. Mounted on the shaftd above the same disk is a member 42 of roughly bell crank outline, said member being loosely mounted thereon and not ordinarily rotating with theV shaft. Lastly mounted on the end of the shaft is a long channelled lever 44 which is also loosely mounted but which is retained in its proper position by a spring member 46 and a pin 48 through the shaft. This disk 38 serves as alignment with the opening through which the` rod |4 projects. A hollow sleeve 52 encases the v outer end of the rod |4 and forms a bushing for the same in the plate 28, said sleeve extending through and terminating in a pin 54 which extends through the opening 50 in the channelled member 44 which maintains the channelled member above the end of the member 52 but permits the shoulder 56 on the same to abut the lower surface of the member 44 and to raise it upon longitudinal movement of the shaft |4. The sleeve member 52 fits the shaft |4 loosely so that there may be relative motion between the two. A split member 58 encompasses the shaft |4 below the member 52 and there are provided a plurality of spring members 60 which are connected -to the inner end of the member 52 and tend to press the split member 58 against the rod |4 in such a manner as to cause a friction drive so that under normal conditions the split member 58 and the connected sleeve 52 will move with longitudinal movement of the shaft |4 but when a..y abutment is reached, such as the shoulder on the member 52 contacting the plate 28, there may be relative movement between the shaft |4 and the member 58 and sleeve 52 to prevent destruction or distortion of the apparatus.

In the sleeve 52 and below the plate 28 there is cut a circular groove 82 within which lies an in` sulating member 64 and in the latter is embedded one end of a contact arm 66 the opposite end of said arm being supported and spaced from two stationary contacts 68 and l0 by insulating block 12 on a bolted support 14. The stationary arms 68 and 10 carry contact; points |14 and |16, respectivelyrwhich engage with a pair of movable contact points 16 on the arm 66 so that as the sleeve 52 moves back and forth longitudinally with movement of the shaft I4, it closes either the upper or the lower contacts as viewed in Figure 5. These stacks of stationary and movable contacts are conventional and similar to the type used in telephone installations and are connected into their various circuits by suitable connections to cables such as 18.

As above mentioned, the pin 54 on the end of the sleeve 52 extends through an opening 50 in the angular member 44, the latter member overlying the member 42 and having two pressed out tips 80 at diametrically opposite points and directed downwardly to contact the upper surface of the disk 42 so that the two, that is, the member 44 and the member 42, lie parallel. Also bent downwardly from the face to project from the surface of the member 42 is an extending tip 82 which under normal circumstances lies adjacent the upper face of the disk 38 and which may under certain circumstances engage in a slot 84 provided in the disk.

One arm of the member 42 extends to one side as shown at 86 and has a raised flange 88 on the outer end which is adapted to contact the insulated end 80 of an arm 92, the opposite end of which is rigidly connected in an insulating block 84 which also supports a substantially stationary arm 86. The insulated end 80 has a slot 9| therein which will allow one portion of the flange 88 to pass thereinto when the arm 86 moves in a counterclockwise direction as shown in Figure 2. This will allow the arm 92 to move outwardly to the right but only until the end 90 contacts the .remainder of the flange 88 which is at right angles to the portion extending through the opening 9| and thus acts as a stop.

A spring bar 93, anchored to the frame by a bracket 95, bears against the member 42 to bias it to a position normally allowing the safety switch to close. The arms 92 and 96 carry contacts 98 and |00 respectively and the opposite ends of the arms are connected to suitable cables in the circuit as shown at |02. These two contacts provide a safety switch which is opened by outward movement of arm 92 and their opera tion will be later described.

The general outline of the disk 38 is provided with a notch |04 which is also an index for the starting position of the disk. In this notch 04 in the deenergized position is the insulated end |06 of a movable arm |08 which is supported in an insulated block assembly ||0 which also supports a substantially stationary arm ||2 having there on two separate contacts ||4 and H6 which engage with a pair of contacts |20, the latter not being insulated from each other on the arm |08. Also supported in the insulating block ||0 is a movable arm |22 and a stationary arm |24 carrying thereon contacts |26 and |28, the end of the arm 22 bearing down upon the insulating block |06 so that the same is also moved when the disk 38 begins to rotate. The contacts |28 and |26 provide the ignition switch and contacts I4, ||6 and I 20 provide a cammed interlocking switch with the stack switch.

Projecting from the lower surface of the disk 38 is a pin |30 which at one period of its rotation is adapted to contact with the insulating end |32 of the movable arm |34 supported in an insulating block assembly |36 between two substantially stationary arms |38 and |40, each of the outer arms carrying contacts |42 and |44 respectively to engage with opposite contacts |46 on the movable arm |34. The object of this switch is to provide only momentary contact between points |42|44, movable contacts |46 being merely to form a momentary contact between the other two when vibrating due to release by the pin. The contacts 46 are not connected into any circuit. Both of the insulating blocks ||0 and |36 are supported in any suitable manner on the upper or outer face of the plate 28.

Mounted between the plate 28 and insulating plate 20 at the opposite end from the motor 34 is a relay coil |48 and directly over the core of the relay is a movable armature |50 spring biased by spring |52 to open position and which when energized closes its two contacts |54 and I 56 and at the same time allows holding contacts |51 to close. There is also an extension |58 upon the armature which extends up to and supports the lower surface of the angular member 44 so that when the relay is deenergized this arm |58 will support the member 44 in parallelism with the member 42 and the disk 38. However, when the relay is energized to close its contacts, this support is withdrawn for a purpose to be described.

'I'he device so far described is what is normally termed a master control and is adapted to be applied in a position whereby the bimetallic element such as' shown at |2 is adapted to project within the furnace so that the heat of combustion may be applied thereto. 'Ihe backing plate 4 supports a cover |60 which will enclose the apparatus and prevent dirt, etc., fromclogging the operation.

The operation of this device in the circuit such as that shown in Figure 6 will be best understood by referring to the wiring diagram' 4in which are shown diagrammatically the other necessary items to complete operation. A supply |62 is provided which supplies the primary |64 of a transformer, the secondary |66 lof which ysupplies the main portion of the control circuit. Directly connected across the supply line |62 is a burner motor at |68 having in series therewith a motor switch |54. Also directly across the line and in parallel with the motor circuit is an ignition circuit including the ignition transformer |10, a pair of relay contacts |56 and a pair of ignition contacts |26 and |28.

In the low voltage circuit and in series with the secondary |66 of the transformer there is a room thermostat |12 and the stack switch movable contact 16 which cooperates with either stationary contact |14 or |16. In series with the stack switch contact |14 is the timing motor 34 and in series with the hot contact '|16 is the momentary contact |34 and the contact ||6 which is operated by the camming movement of the y the motor to discharge -chamber and also the rotated disk in cooperation with the vmovable contact |20. Also in series with the cold contact |14 of the which also cooperates with |20 of the camming disk.

Connected between the secondary and the momentary contact switch |34 is the relay |48 and in series with the momentary contact |34 the contact ||6 are holding contacts |51 for the relay |48. Also connected in the main line ahead of the transformer |64 are safety switch contacts 38 and |00 which upon opening cause the whole system to be deenergized.

The operation of the system therefore is as follows: The safety switch contacts 88 and |00 are normally closed so that the transformer |64 is energized and with the stack in its cold position so that contacts 16 and |14 engage, when the room thermostat |12 closes its circuit a timing motor is energized through an obvious circuit as follows: Secondary |66, room thermostat |12, contacts 16|14, timing motor 34 and secondary |66. This causes the control motor motor tostart in operation and therefore the disk 38 rotates in a counterclockwise direction as viewed in Figure 2which, due to the camming action of the notch |04, presses the insulating block |06 out to the left and closes the ignition contacts |26 and |28 and also presses the movable contact |20 against both contacts ||4 and the movable contact As noted hereabove, the timing motor 34 is initially energized on closure of the room thermostat |12 through thecontacts 16 and |14 ofthe stack switch which are closed when the ystack is cold. As soon as the timing motor starts, the A rotation of the disk 38 closes contacts |20 and I|4 by the cam operation of block |06 which establishes a further circuit from the room thermostat to the timing motor to sustain the energization thereof after the stack switch contacts 16 and |14 open on establishment of combustion for one revolution when the block |06 falls into the notch |04 and contact |20 moves away from contact ||4.

At the same instant the pin forces the arm |32 to the left and then as it passes the 'tip |32 springs back and is designed so as to cause stack switch is the contact ||4 and A a momentary circuit from contact |44 through contact |46 to contact |42 so that the relay may be momentarily energized through the following circuit: |66, |12, |20, ||6, |40, |44, |46, |42, |48 and back to the secondary |66. As the relay snaps in it closes its own holding contact |61 and therefore remainsv energized as long as the room thermostat |12 calls for heat, if, of course, the normal sequence is maintained with regard to the operation. It also closes two sets of contacts |54 which close the motor circuit and allow oil into the combustion closure of the contacts |56 closes the ignition circuit so that at the same time a spark is provided to ignite the fuel.

The device therefore continues to o'perate in what may be termed the initial or instigatlng stage and the disk 38 proceeds to rotate but it'is to be noted that with the energization of the relay |48 the arm |58 has been withdrawn from supporting the channelled member 44 and therefore this member presses against the member 42 through the two bent down tips 80 which press inwardly in turn on the face of the disk 38 and exert this pressure on the downwardly bent portion 82. As the furnace-heats normally the rod |4 will be caused to move inwardly and the shoulder 56 on the sleeve 52 will abut the lower surface of the member 44 and lift it relieving the inward pressure of the member 82 on the disk 38 so that as the slot 84 rotates past the position of the member 82 this projecting member will not be forced into the slot and the disk 38 may continue to rotate to its normal stopping position which is at the end of 360.

If, however, the furnace has not heated through some fault, the projection 82 will .extend into the opening 84 due to the fact that the elongated or over-balanced member 44 presses downwardly on that portion of the member 42 to so force it in and thereafter the member 42 will rotate with the disk 38 which will of course cause it to turn the arm 86 whose iiange 86 will pull the end of the lever 82 in a counterclockwise direction to trip into opening 8|' to break the safety switch contacts. This will of course deenergize the whole system and necessitate manual reset by button |18. If, however, the furnace has ignited, as above stated, the disk 38 will rotate through to the end of its 360 and the relay will then be maintained operative alone through a circuit as follows: |66, |12, 16, |16, |51, |48 back to |66.

When a sufficient amount of heat has been supplied to the location to be heated the thermostat |12 will open this circuit and cause a deenergization of the device. If the device is in operation under normal conditions and there is a momentary current failure, the switch points |51 which 'y portion of the switches, relay means for operating a further portion, temperature responsive means for operating the remainder and separate mechanical interlocking means between the relay and temperaturev responsive means and one of 4 2,254,484 the switches to alter and affect the operation of means for controlling safety switch operation, a

said last named switch by the rotatable means. relay on said support, an armature attractibie 2. In a master control for a uid fuel burner. thereby, said armature having an extension ena. support, a timed switch mounted thereon, rogaging the safety switch operating means to contatable means operating said switch, a safety 5 trol in combination with the temperature responswitch, means operated by the rotatable means sive means the action of the safety switch.

for operating the safety switch, temperature responsive means contacting the last mentioned WILLIAM H. HUTCHINS. 

